President Barack Obama tries to calm international anger over snooping as news breaks of German leader’s phone being bugged for over 10 years.

German spy chiefs will travel to Washington shortly to talk with US officials about the spying allegations that have so angered Europe, including whether Chancellor Angela Merkel's cellphone was monitored by the National Security Agency. (Oct. 25)

WASHINGTON—The United States may have bugged Angela Merkel’s phone for more than 10 years, according to a news report on Saturday that also said President Barack Obama told the German leader he would have stopped it happening had he known about it.

Germany’s outrage over reports of bugging of Merkel’s phone by the National Security Agency (NSA) prompted it to summon the U.S. ambassador for the first time in living memory, an unprecedented post-war diplomatic rift.

Der Spiegel said Merkel’s mobile telephone had been listed by the NSA’s Special Collection Service (SCS) since 2002 — marked as “GE Chancellor Merkel” — and was still on the list weeks before Obama visited Berlin in June.

In a document cited by the Der Spiegel, the NSA said it had a “not legally registered spying branch” in the U.S. Embassy in Berlin, the exposure of which would lead to “grave damage for the relations of the United States to another government.”

From that embassy listening post, NSA and CIA staff were tapping communication in the Berlin’s government district with high-tech surveillance.

Quoting a secret document from 2010, Der Spiegel said such branches existed in about 80 locations around the world, including Paris, Madrid, Rome, Prague, Geneva and Frankfurt. The magazine said it was not clear whether the SCS had recorded conversations or just connection data.

Obama apologized to Merkel when she called him on Wednesday to seek clarification on the issue, Der Spiegel wrote, citing a source in Merkel’s office. Frankfurter Allgemeine Sonntagszeitung also said Obama had told Merkel he had not known of the bugging.

Both he and Secretary of State John Kerry are trying to calm international anger over classified disclosures by former NSA contractor Edward Snowden. Snowden’s revelations about NSA tactics, which allegedly include tapping as many as 35 world leaders’ cellphones.

Merkel’s spokesman and the White House declined comment Saturday.

“We’re not going to comment on the details of our diplomatic discussions,” said Caitlin Hayden, a spokeswoman for the National Security Council at the White House.

This latest international embarrassment for the United States comes as about 2,000 domestic protesters marched on Capitol Hill in Washington on Saturday to protest against the NSA’s vast online surveillance within the U.S. itself.

Germany will send intelligence chiefs to Washington next week to seek answers on the allegations around Merkel’s phone.

In other developments Saturday:

Kerry flew to Rome and Paris, ostensibly to talk about Mideast peace, Syria and Iran, but was confronted by outrage over U.S. spying abroad.

“The magnitude of the eavesdropping is what shocked us,” former French foreign minister Bernard Kouchner said in a radio interview. “Let’s be honest, we eavesdrop too. Everyone is listening to everyone else. But we don’t have the same means as the United States, which makes us jealous.”

The British ambassador to Lebanon, Tom Fletcher, tweeted this week: “I work on assumption that 6+ countries tap my phone. Increasingly rare that diplomats say anything sensitive on calls.”

Diplomatic relations are built on trust. If America’s credibility is in question, the U.S. will find it harder to maintain alliances, influence world opinion and seal trade deals.

Two Western diplomats say U.S. officials have briefed them on documents obtained by Snowden that might expose the intelligence operations of their respective countries and their level of co-operation with the U.S.

The two diplomats said officials from the Office of the Director of National Intelligence continue to brief them regularly. They spoke on condition of anonymity.

The Washington Post, which first reported on the matter Thursday evening, said some of the documents Snowden took contain sensitive material about collection programs against adversaries such as Iran, Russia and China. Some refer to operations that in some cases involve countries not publicly allied with the United States.

The Post said the process of informing officials about the risk of disclosure is delicate because in some cases, one part of the co-operating government may know about the collaboration, but others may not.